The present invention, in some embodiments thereof, relates to active noise cancellation/control and, more specifically, but not exclusively, to active noise cancellation/control for headphones based on a combination of aural and nonaural noise signals.
In active noise reduction systems, also known as active noise cancellation/control (ANC) systems, the same loud speakers, in particular loud speakers arranged in the two earphones of headphones, are often used for both noise reduction and reproduction of desirable sound such as music or speech. ANC may be referred to herein as active noise reduction.
Modern ANC is generally achieved through the use of analog circuits or digital signal processing. Adaptive algorithms are designed to analyze the waveform of the background aural or nonaural noise, then based on the specific algorithm generate a signal that will either phase shift or invert the polarity of the original signal. This inverted signal, in anti-phase, is amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform, creating destructive interference. This effectively reduces the volume of the perceivable noise.